<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div id="app">
  <label>
    <input type="checkbox" value="篮球" v-model="ball">篮球
    <input type="checkbox" value="足球" v-model="ball">足球
    <input type="checkbox" value="排球" v-model="ball">排球
    <input type="checkbox" value="铅球" v-model="ball">铅球
  </label>
  <hr>
  <label v-for="item in balls" for="a" >
    <input type="checkbox" id="a" :value="item" v-model="ball">{{item}}
  </label>
  <h1>{{ball}}</h1>

</div>

<script src="../js/vue.js"></script>
<script>
  //let(变量)和const(常量)
  const app = new Vue({
    el: '#app',
    data: {
      message: '中国牛蛙！',
      ball: [],
      balls: ['篮球','足球','排球','火球','水球']
    }
  })
</script>
</body>
</html>